A new teaser image on the official Call of Duty website has...
Matchmaking now based on Latency & Ping, not region in Black Ops 2
David Vonderhaar has just confirmed via Twitter that Black Ops 2 MP’s matchmaking system will be based upon your latency and ping, not your region.
This is a new feature, as MW3 does matchmaking based upon regions. This may help with connection issues and allow better connectivity with host.